Networks that primarily utilize data link layer devices are often referred to as layer two (L2) networks. A data link layer device is a device that operates within the second layer of the Open Systems Interconnection (OSI) reference model, i.e., the data link layer. One example of a common L2 network is an Ethernet network in which end point devices (e.g., servers, printers, computers) are connected by one or more Ethernet switches. The Ethernet switches forward Ethernet frames, also referred to as L2 communications or L2 packets, to devices within the network. As the Ethernet switches forward the Ethernet frames the Ethernet switches learn L2 state information for the L2 network, including media access control (MAC) addressing information for the devices within the network and the physical ports through which the devices are reachable. The Ethernet switches typically store the MAC addressing information in MAC tables associated with each of their physical interfaces. When forwarding an individual Ethernet frame, an ingress port of an Ethernet switch typically broadcasts the Ethernet frame to all of the other physical ports of the switch unless the Ethernet switch has learned the specific physical port through which to the destination MAC address devices is reachable. In this case, the Ethernet switch forwards a single copy of the Ethernet frame out the associated physical port.
One type of large area L2 network connectivity being developed is referred to as “Metro Ethernet” in which Ethernet is used as a metropolitan access network to connect subscribers and businesses to a larger service network or the Internet. Various types of Ethernet services have been defined to provide different forms of connectivity. For example, so called “E-LINE” service, also known as Virtual Leased Line (VLL) or Ethernet Private Wire Service (EPVS), provides point-to-point (P2P) connectivity. “E-LAN” service, also known as Virtual Private LAN Services (VPLS) and Transparent LAN Services, provides multipoint-to-multipoint (MP2MP) connectivity in which there is no communication restriction between devices. A third type of metro Ethernet service, referred to as “E-TREE” service, has recently been defined in which Ethernet communication is constrained to point-to-multipoint (P2MP). With E-TREE service, each endpoint L2 device is designated as either a root or a leaf L2 devices designated as roots are permitted to communicate with all other endpoints on the E-Tree. However, L2 devices designated as leafs on the E-tree are permitted to communicate only with L2 devices designated as root devices.